1. Technical Field
The present invention relates generally to bandwidth management in digital loop carrier (DLC) systems and, more particularly, to bandwidth management including a scheme for optimized linked list processing.
2. Description of the Related Art
DLC systems have been an important part of local exchange carrier line deployment for over 15 years. They reduce the copper cabling used in local loops, which comprise the physical connection between a subscriber""s premises and the telecommunications network provider. A DLC system consolidates multiple individual subscriber telephone lines into one or more copper or fiber carrier lines extending from the subscriber area to the network provider central office (CO). DLC systems thereby enable network providers to leverage investments in copper cable in the field by allowing it to transport more subscribers in larger geographic areas.
It has become increasingly important to scale networks to higher speed technologies such as, e.g., digital subscriber line (xDSL) technology, integrated synchronous digital network (ISDN) and other services. These technologies allow data to be transmitted over standard copper cable at speeds of several megabits of data per second. Many factors are driving the need for faster transport capabilities, the most significant of which is increased Internet usage by subscribers.
The resulting increased network traffic has caused bottlenecking in existing DLC systems because of the finite bandwidth capacity of the carrier line infrastructure leading to the CO. A tremendous need thus exists for increasing the capacity and flexibility of existing carrier line infrastructure.
A known method for increasing available bandwidth in existing communication networks comprises compressing all loop traffic (namely, both voice frequency and data) using compression techniques such as adaptive pulse code modulation (ADPCM) and other compression algorithms. While voice signals can generally be compressed without significant degradation, compression has a detrimental effect on the quality and bit rate of data transmission. Consequently, compression techniques are not widely used in loop systems.
A primary object of the invention is to provide a method and apparatus for intelligently and efficiently managing bandwidth in a DLC system by rapidly identifying and selectively compressing signals that can be compressed without significant degradation.
Another object of the invention is to provide a bandwidth management scheme for a DLC system that includes a linked list optimization scheme for efficiently identifying calls requiring analysis for compressibility.
A further object of the invention is to provide a bandwidth management scheme for a DLC system that includes a linked list optimization scheme containing an active scan list of calls requiring analysis for compressibility.
These and other objects are accomplished by a method and apparatus for efficiently managing bandwidth in a DLC system. In a preferred embodiment, the system includes service cards connectable to at least one transport card having a given bandwidth capacity. Each of the service cards supports multiple subscriber channels. Upon initiation of a first call, the system allocates the call to a given time slot of the transport card. The given time slot is assigned a given default bandwidth, e.g., 64 kbps. While the first call is in progress, the system determines whether the call is voice or data (e.g., modem). If the first call is voice, the system may selectively reduce the given default bandwidth allocated to the first call if necessary to ensure that a second call, if initiated while the first call remains in progress, can be assigned the given default bandwidth. Thus, each new call is ensured of getting at least the default bandwidth when initiated.
Efficient bandwidth management is provided by an inventive linked list optimization scheme, which includes a linked list of words, each associated with a time slot. The linked list is periodically searched to identify words whose associated time slots have not been analyzed to determine if a call allocated to the time slot is a voice or data call. For rapid processing, only the identified time slots are analyzed. Thus, the present invention optimizes linked list processing by the DSP by avoiding unnecessary time slot analysis. Accordingly, while the system may be handling thousands of time slots at a given time, the DSP analyzes only those time slots whose analysis has not been completed. The system is thereby able to more quickly and efficiently process the time slot linked list.
The foregoing has outlined some of the more pertinent objects and features of the present invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or modifying the invention as will be described. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the following Detailed Description of the Preferred Embodiment.